Processes for carbonylating olefinically unsaturated hydrocarbons are known from U.S. Pat. Nos. 3,887,595 issued June 3, 1975 and 4,172,087 issued Oct. 23, 1979 inter alia.
In U.S. Pat. No. 3,887,595 a process is described for the carbonylation of olefinically unsaturated hydrocarbons of 2 to 30 carbon atoms, free of acetylenic unsaturation and conjugated olefinic unsaturation with carbon monoxide and with at least one hydroxyl compound, selected from a group consisting of water, alkanol having 1 to 20 carbon atoms, carboxylic acid having 2 to 20 carbon atoms and mixtures thereof, in the presence cf a catalyst, with formation of predominantly straight-chain products, using as the catalyst a composition essentially consisting of:
(a) a zero valent noble metal phosphine complex wherein the metal consists of palladium or platinum and is surrounded by 1 to 4 ligands, consisting of phosphines comprising three optionally substituted hydrocarbon moieties of 1 to 20 carbon atoms, free of aliphatic carbon-carbon unsaturation and selected from the group formed by alkyl, unsubstituted phenyl, monosubstituted alkyl and,
(b) from about 10 mole to about 150 mole of the phosphine per mole of the metal phosphine complex concerned.
From U.S. Pat. No. 4,172, 087 a process is known for the simultaneous preparation of two groups of unsaturated carboxylic acids and ester thereof from aliphatically conjugated diene substrates containing from 4 to 8 carbon atoms wherein:
(a) every two moles of the aliphatically conjugated diene concerned are mixed with a three-component mixture consisting of
(i) at least a catalytic quantity of a palladium catalyst consisting of either one or more palladium halide salts in combination with one or more monodentate tertiary phosphorus containing donor ligands, or one or more palladium halide free salts in combination with one or more multidentate, tertiary phosphorus containing donor ligands; PA1 (ii) at least one molar equivalent of a hydroxyl group containing co-reactant, selected from the group consisting of water or an aliphatic alkanol containing 1 to 12 carbon atoms; and PA1 (iii) an N-heterocyclic amine base in order to form a reaction mixture;
(b) the reaction mixture is pressurized with sufficient carbon monoxide to satisfy the stoichiometry of the carbonylation reaction,
(c) the pressurized reaction mixture is heated up to temperatures of 30.degree. C. to 150.degree. C. until substantial formation of the desired aliphatic carboxylic acid derivatives has been achieved, and
(d) the unsaturated carboxylic acid derivatives concerned that occur therein are isolated.
Preferably, 1,3-butadiene is used as a starting material, while pyridine, alkylated pyridines, quinoline, lutidine, picoline, isoquinoline, alkylated quinolines and isoquinolines and acridine or N,N-dimethylaniline, N,N-diethylaniline, N,N-diethyltoluidine and N,N-dibutyltoluidine and N,N-dimethylformamide and N-methyl-2-pyrrolidone can be used a N-heterocyclic amine base.
It will be clear that the processes described hereinbefore do not relate precisely to the selective conversion of conjugated unsaturated compounds nor, in particular, to the selective preparation of 3-pentenoic acid and derivatives thereof, which is becoming an increasingly important base material for organic syntheses (for example, for the preparation of adipic acid and derivatives thereof), have been diverted away from the methods described hereinbefore.
Most of the known butadiene conversion methods are, moveover, characterized by the use of relatively large concentrations of hydrochloric acid or other hydrohalogenic acids and otherwise rigorous reaction conditions, whereby supplementary, mostly cost-increasing measures have been necessary on account of safety and apparatus (corrosion).
An improved process has now been surprisingly found for the selective conversion of conjugated dienes in the liquid phase and particularly for the selective preparation of 3-pentenoic acid or derivatives thereof by the conversion of 1,3-butadiene and analogous conversions of isoprene, 2-methylbutadiene, 1,3-hexadiene and analogous conversions of isoprene, 2-methylbutadiene, 1,3-hexadiene, 2,4-hexadiene, 2,4-heptadiene and higher homologues, with a generally increased ccnversion rate, in the presence of a characteristic catalyst system.